This invention relates to a lightweight, wearable, and, in some embodiments, balanced active tremor control system which, in one embodiment, features a tremor suppressing wrist cuff.
Uncontrollable tremors afflict a significant portion of the population adversely affecting an individual""s ability to perform physical tasks such as eating, drinking, reading, and walking.
Moreover, even when tremor causing medical problems are not present, even slight normal tremors can adversely effect an individual""s ability to precisely perform certain delicate functions including using surgical instruments and performing technical procedures and operations.
As a result, those skilled in the art have long sought to control tremors. Traditional vibration isolation or suppression systems incorporating actuators and used in connection with vibrating machinery do not work well when used in conjunction with human limbs subject to tremors because there is no fixed in place structure available on which to mount the actuators for the actuator reaction force.
In U.S. Pat. No. 5,058,571, hereby incorporated herein by this reference, a hand-held gyroscope device is shown to be firmly held against the backside of the human hand in an attempt to reduce or eliminate the effect of naturally occurring tremors. Unfortunately, the resulting device hinders all motion instead of just damping tremors.
Passively damping tremors, for example, by using a mass coupled to a wrist by resilient members may control tremors but would have to be specifically tuned to meet each individual""s needs and also presents certain other disadvantages.
Any wearable, active vibration control device, besides being effective at controlling tremors, must be lightweight and preferably balanced and not interfere with an individual""s intended movements.
It is therefore an object of this invention to provide a lightweight tremor control system.
It is a further object of this invention to provide a wearable active tremor control system.
It is a further object of this invention to provide such an active tremor control system which can be balanced.
It is a further object of this invention to provide a tremor suppressing wrist cuff.
It is a further object of this invention to provide an active tremor control system which is more effective at controlling tremors.
It is a further object of this invention to provide such a system which can be worn on the wrist, the forearm, the hand, or the leg.
It is a further object of this invention to provide such a system which can be used by people with medical problems which cause tremors.
It is a further object of this invention to provide such a system which can be used by people with no tremor causing medical problems but who need to manipulate instruments or devices more accurately.
It is a further object of this invention to provide such a system which can be attached directly to an instrument or device.
The invention results from the realization that a wearable device for actively controlling tremors using a proof mass stabilizer can only be connected to the wearer""s body part (e.g., the wrist) and, that being the case, there is no fixed structure on which to mount the actuators but, by employing a wearable proof mass frame housing the actuators which then act on the mounting structure, the actuators themselves become proof masses for the system resulting in a lightweight, wearable, and balanced tremor control system.
This invention features a lightweight, wearable, and balanced active tremor control system comprising a mount; a proof mass frame moveable with respect to the mount; at least one actuator on the proof mass frame for imparting a force on the mount; a motion sensor for detecting displacement of the mount; and a controller for driving the actuator in response to the motion sensor. In the preferred embodiment, there are two voice coil linear actuators orthogonally oriented on the proof mass frame and two accelerometers orthogonally oriented on the mount.
The preferred proof mass frame includes a central section interconnected with the mount and a pair of arms depending therefrom and a weight attached to the end of each arm. The central section of the frame includes two angled actuator housings and the mount is unitary in construction and spans the central section of the proof mass frame. In the preferred embodiment, the mount includes two planar side surfaces and a top planar surface. Two ball slide mechanisms interconnect the proof mass frame and the mount. The housing portion of each ball slide mechanism is fixed with respect to the mount and the sliding arm portion of each ball slide mechanism is physically connected to an actuator.
Typically, the accelerometers are mounted with respect to the mount such that the input axis is parallel to the force axis of the actuators. Further included may be means for fixing the position of the proof mass with respect to the mount and for sensing the position of the proof mass frame with respect to the mount, e.g., two linear voltage displacement transducers, one portion of each attached to the mount, the other portion of each attached to the proof mass frame.
The tremor suppression wrist cuff of this invention features a wrist mount including a top surface and angled surfaces disposed over the ulna and radius bones of the human wrist, respectively; a proof mass frame moveable with respect to the wrist mount; and a pair of actuators each connected to the proof mass frame and an angled surface of the wrist mount to apply force to the angled surfaces of the wrist mount and to the ulna and radius bones of the wrist. Typically, the proof mass frame includes angled actuator housings and each actuator has a magnet disposed in an actuator housing. A pair of ball slide mechanisms each include an arm slidable in a housing to allow the actuators to move laterally. Each actuator has a coil mounted to an arm and the housing of each ball slide mechanism is mounted to an angled surface of the wrist mount. Also included may be a pair of guide pins slidably disposed through the proof mass frame and each connected on one end to an adapter plate which secures the coil of each actuator to its respective arm of the ball slide mechanism to guide the actuators. A pair of transformers each including a core may be mounted to the top surface of the wrist mount with the moveable part mounted to an adapter plate for sensing and adjusting the position of the proof mass frame relative to the wrist mount. Typically, the proof mass frame includes a pair of arms depending therefrom and there is a weight attached to each arm so that the center of mass of the wrist cuff is at the center of the wrist.
The active tremor control system of this invention features a mount attachable to a device or a body part; a proof mass frame moveably joined with respect to the mount; at least one sensor for detecting vibrations of the mount; and at least one actuator disposed to apply a force to the proof mass frame with respect to the mount to thereby suppress vibrations of the mount. In the preferred embodiment, there are two independently driven actuators for adjusting the position of the proof mass frame with respect to the mount.
In the preferred embodiment there are two sensors, one accelerometer and one linear voltage displacement transducer (LVDT). The LVDT provides a signal to the controller that commands the actuator to keep it nominally centered in the range of actuation. The purpose of this is to counteract the force of gravity. The accelerometer provides a signal to the controller that commands the actuator to quell the tremors.